Contact resistance properties between nanotubes and various metals from quantum mechanics

We report on the interfacial structure, the current-voltage (I-V) characteristics, and contact resistance of metal electrode-carbon nanotube contacts for five metals, Ti, Pd, Pt, Cu, and Au, based on first-principles quantum mechanical density functional and matrix Green's function methods. We find that Ti leads to the lowest contact resistance followed by Pd, Pt, Cu, and Au. The sequence, Ti > Pd > Pt > Cu > Au, correlates well with the predicted cohesive strength of the electrode-carbon interface. In addition Ti leads to linear I-V characteristics up to similar to 1 V, suggesting an Ohmic contact for both metallic and semiconductor nanotubes. However, the high reactivity of the Ti electrode at the contact to the nanotube distorts the nanotube structure.